In this study the consequences of exacerbations will be visualized by high resolution computed tomography (HRCT) scan at functional residual capacity (FRC) and total lung capacity (TLC) as taken during an episode of exacerbation and after recovering. Changes in HRCT based airway dimensions and computational fluid dynamic (CFD) -based resistance values will be correlated with changes in patient reported outcomes (PROs) and lung function tests recorded at the same time.

Inclusion Criteria:

• Male or female, ≥ 40 years old
• COPD as defined by the global Initiative on obstructive lung disease4
• Post-bronchodilator FEV1/FVC < 70% AND post-bronchodilator FEV1 <80%pred as documented in the last 5 years.
• Smoking history of at least 10 pack-years
• At entry in the study experiencing an exacerbation defined as an acute change in the patient 's baseline dyspnea, cough, and/or sputum that is beyond normal day to day variations, and that necessitates the administration or doubling of systemic corticosteroid treatment.
• Patients must be able to understand and complete protocol requirements, instructions, questionnaires and protocol-stated restrictions.
• Written and signed informed consent

Exclusion Criteria:

• Pregnant or lactating females
• Patient diagnosed with asthma
• Patient with pneumonia as defined radiologically at the start of the exacerbation
• Patient with a history of or presence of lung cancer
• Patient with an indication for non-invasive ventilation
• Patient unlikely to comply with the protocol or unable to understand the nature, scope and possible consequences of the study.
• Patient who received any investigational new drug within the last 4 weeks prior to visit 1.